March 25, 2014

James Nechols, professor of entomology, and Lindsey Milbrath, USDA-ARS, Ithaca, N.Y., and an alumnus of Kansas State, have recently published an important review article in the international journal Biological Control vol. 72, pages 82-90.

The article provides a look back and a look forward at the role of interactions between multiple plant-feeding species in the biological control of weeds. The paper, "Plant-mediated interactions: considerations for agent selection in weed biological control programs," describes the effects of feeding by one herbivorous species, arthropod or plant pathogen, mediated through the plant to affect another species of herbivore, arthropod or plant pathogen.

Although such interactions are widely noted in the ecological literature, they have not been considered deeply in the biological control literature, where the assumption has often been that multiple herbivore species of whatever type feeding on a plant produce an additive effect on the plant. This has led to something of a "the-more-the-merrier" approach in utilizing natural enemies to suppress weeds. However, plant-mediated effects on the various herbivore species may actually result in a net benefit for the weed, nullifying the biological control efforts.

Nechols and Milbrath argue convincingly that understanding these species-to-species effects mediated through plants is critical for planning and executing effective weed biological control programs and, recognizing the more complicated evaluation protocols necessary to acquire this information, propose workable protocols for evaluation and decision-making for release programs. Although at one level, the proposed procedures would add to the workload preceding release of candidate organisms for biological control of weeds, on another level, understanding these interactions may play a critical role in establishing a firm predictive base for biological control of weeds making the work more efficient and successful.

This article represents an important step forward for the biological control community at a time when sustainable practices for managing pests are becoming increasingly vital on a global scale.